Apparatus for the production of music



" Feb. 23, 1931.-

w I lilllml B. F. MIESSNER ET AL APPARATUS; FOR THE PRODUCTION OF MUSIC Original Filed Dec. 1, 1933 s Sheets-Sheet 1 Feb. 23, 1937. v a. F.-MIESSNER ET AL APPARATUS FOR THE PRODUCTION OF MUSIC 3 Sheets -Sheet 2 Original Filed Dec. 1, 1935 Feb. 23, 1937.

B. MIESSNER ET AL APPARATUS FOR THE PRODUCTION OF MUSIC Original Filed Dec, 1, 1933 3 Sheets-Sheet 3 7 M mw 3%. m 7

INVENT RS:

Patented Feb. 23, 1937 UNITED STATES APPARATUS FOR THE PRODUCTION OF MUSIC Benjamin F. Miessner, Millburn, and Charles T. Jacobs, New Providence, N. J., assignors to Miessner Inventions, Inc., a corporation of New J crsey.

ApplicationDecember 1, 1933, Serial No. 700,396 Renewed October 10, 1936 20 Claims.

This invention relates to musical'instruments, and has special reference to those in which the output sound is translated from the vibrations of l a tuned vibrator or of a plurality of tuned vibrators.

In the U. S. Patent No. 1,915,859, issued to us June 27, 1933, there was shown and claimed an instrument wherein a mechanico-electric translating system associated with each vibrator, and adapted'to translate vibrations thereof into electric oscillations which were in turn translated into sound, was maintained normally in a given condition of operativeness or of translation efficiency, and was caused gradually (as distinguished from abruptly) to assume another condition or efficiency upon the inception of vibration of the associated vibrator. If for example the first mentioned efficiency was of zero value and the second of finite value, the oscillations produced by the translation of vibration would give rise upon their translation into sound to a tone simulating that of a wind or similar instrument, even though the inception of the vibration were abrupt. This invention contemplates particu larly instruments wherein this and similar arrangements are incorporated.

In the mentioned patent the instrument to which the described arrangements were applied was a piano. Therein the mechanico-electric translating system associated with the string (or strings) for. each different note was caused to assume the second mentioned efficiency just after impact of the hammer with suchstring, and to retain this second efliciency only as long as F the associated key remained depressed. Therefore the conventional loud (more aptly and hereinafter termed sustaining) pedal and the conventiona sostenuto pedal, although available to maintain the string in vibration after associated key release, were not operative to maintain the efliciency at the second value, the efficiency returning to its first value promptly upon key release. Thus in the mentioned example an output tone could not be prolonged by either pedal after key release.

' proved instrument whereby'there are produced output tones having i\nceptions of nature modi- ElSSUiZD fied from that of the inception of the vibrations from which said tones are" translated.

In the mentioned patent electric circuits with suitable switches included therein, were employed in the control of the mechanico-electric translation efliciency, and it is a particular ob-. ject of the instant invention to provide improved such circuits. Another particular object is the provision of such circuits in convenient and compact association with the conventional parts of a piano. v Other and allied objects will more fully appear from the following description and the appended claims.

In the description reference is had to the accompanying drawings, of which,:--

Figure 1 is a vertical cross-sectional view through a portion of an instrument of the grand piano type, illustrating an embodiment of the invention, this figure showing partially diagrammatically the mechanico-electric and electroacoustic translating apparatus;

Figure 2 is a schematic diagram of the electrical circuit of the main portion of Figure 1;

Figure 3 is a view of similar nature to the main portion of Figure 1,-but illustrating a modified embodiment of the invention;

Figure 3a is a cross-sectional view taken along the line 3a of Figure 3 and illustrating in detail a portion of that figure;

Figure 4 is a schematic diagram of the electrical circuit of Figure 3;

Figure 5 is a view of similar nature to the main portion of Figure 1, but illustrating a further modified embodiment of the invention; and Figure 6 is a schematic diagram of the electrical circuit of Figure 5.

Reference being directed particularly to Figfront frame portion la is shown a wrest-plank 39, r

in which may be retained tuning pins 2 which do not contact with the frame. In the rear frame portion lc may be secured insulating bushlngs 3 and therein respectively hitch pins 4. From each tuning pin, under capo or frame portion lb, over a bridge 34 and to a respective hitch-pin is strung a string 5. Along the top rear edge of frame portion la, the bottom of capo or frame portion lb, and the top front edge of frame portion lc may be provided bakelite or other insulatingstrips 6a, 6b and 60 respectively, in order that each string may be completely insulated from the frame I.

All the strings 5 may lie in the same horizontal plane: therefore there appears in the figure the main portion of, and the apparatus 10 associated with, a single string only. The contemplation of a plurality of strings, however, is indicated by the additional illustration of a particular other tuning pin 2' and of the front portion of a particular other string 5' strung to tuning pin 2'.

Each string is excitable by an individual hammer I, having hammer tail 16, shank'8l, sta- I tionary flange I9, and metallic pin 82 pivoting the shank to the flange. For operating the hammers are provided keys 8, each having a horizontal rearward extension 9 jpivoted as at ID; a particular other key, adjacent for example to the one principally appearing in the figure, has been designated as -8' andits pivot as Ill by way of illustration. Each key 8 is operatively connected with a respective hammer through an individual piano action mechanism ll interposed between the key extension 9 and the hammer shank Bl. To the rear of each extension 9 is secured, as by rod 14, a back-check l0 having wooden body ll, leather facing 13, and felt I2 interposed between body and facing. The parts as described in this paragraph are conventional. It will therefore be understood that upon depression of any key 6 its associated hammer I will be propelled toward and caused to strike the associated string 5, immediately rebounding therefrom; and that, unless. the key manipulation be of an extreme staccato nature, the hammer tail [6 upon the rebound will H which passes through common guide rail l5 and is terminally secured to a damper bushing l6. This bushing is pivoted to damper lever l1; and the lever I1 is pivoted by metallic pin 68 to damper flange [8, which is securedto a common rigid portion l9 as by screw 20. The forward end of the bottom surface 69 of each damper lever I1 is very slightly spaced above the rear' upper surface 15 of the extension 9 of the associated key 8, and is therefore adapted to be lifted upon and throughout depression of that key. This obviously liftsthe damper l3 from and thus de-damps the associated string throughout the period of key depression. The parts described in this. paragraph also will be recognized as entirely conventional elements of the grand piano.

Pedals of the conventional sustaining" and sostenuto types are schematically illustrated a7s 2| and 26, respectively, pivoted as at 22 and 7e 21. The pedals are provided with rearward extensions 23 and 28, respectively, and to these extensions are terminally connected rods 24 and 29, respectively, each rod being raised by depression of the associated pedal. -Both rods may 75' pass through rigid base 33. Connected to the.

top of rod 24 is shown bar 25, this bar passing under all of the damper levers l1 so that upon depression of the sustainingpedal 2| all the damper levers will be lifted and all the strings de-damped. The top of rod 29 is connected to a strip 30 hinged along its edge 3| to rigid portion I9, so that upon depression of the sostenuto pedal" 26 the strip 30 will be swung about its edge 3| in a clockwise direction as *that -bushing will be engaged by the upward "swing of strip 30 and will be held raised, together with the associated damper l3, after release of that key and as long as pedal 26 is maintained depressed. It is convenient to consider the sustaining pedal 2! as lifting the damper l3 to a slightly lower position, and to consider the sostenuto pedal 26 as lifting those dampers whose tongues it may engage to a slightly higher position, than that maintained by complete key depression. That the action of the pedals may be so limited there have been shown collars 24a and 29a adjustably secured to rods 24 and 29, respectively, and adapted to impinge upon the bottom of base 33. It will be understood that these particular sustaining and sostenuto pedal arrangements are functionally identical with those conventionally included in the grand piano, and are shown constructionally simplified or modified therefrom only in the interest of simple illustration.

Ingeneral in Figure 1 (as well as in similar succeeding figures) there are shown. in section only mechanical parts common in function to the several-strings and to the therewith associated striking and damping systems; and conversely all such common mechanical parts have been shown in section excepting the pedal system portions 2I--2223-2424a and 26-2|-- 28-29-29a.

In Figure 1 there is also shown the mechanicoelectric translating system. This includes a conductive strip 4| of small cross-section, which may be cemented to the top of a thin bakelite or other insulating strip 42 and thereby maintained in slight spaced relationship to all of the strings. The spacing of strip 4| from the several strings is in general .just sufficient to avoid contact of strip and string under a condition of maximum vibration of the latter; and these'individual spacings are conveniently adjusted by slight up-anddown adjustment of the rear string extremity, as by an individual screw 35 having an annular groove 36 engaging the associated string. A high resistance 43 may connect the strip 4| to the frame I, which is inan electrical sense hereinafter frequently referred to as ground. Means supplying variable D. C. potentials and herein-.

after described is provided between ground and each string; and it will be understood that by this means the minute capacity between strip 4| and each string is charged through resistance .43. The value of. resistance 43 is preferably made high enough to render the charge in each such capacity relatively incapable of rapid variationi. e.; of oscillation variation at a frequency as high as that of string vibration. Therefore oscillatory variation of any of these capacities, produced as by vibration of the associated string, in turn promeans for supplying variable D. C. potentials be,

tween ground and each string-or in other words current source 53.

duces an oscillatory voltage component across the capacity. This component is applied through the potential supplying means, which has a low impedance to alternating currents, to the resistance 43 and appears as an A. C. voltage thereacross.

Across the terminals of resistance 43 may be connected an electrical amplifying and electroacoustic translating system for amplifying and translating into sound such A. C voltages. This system has been shown as comprising in cascade an amplifying tube 44 and associated circuit, amplifier 45, potentiometer or volume control 46, further amplifier 41, and loudspeaker 48. The

circuit associated with tube 44 may comprise a condenser 49 connected between the tube grid and the strip connected extremity of resistance 43; a small bias resistance 50, by-passed by a condenser 51, connected from the tube cathode to the ground extremity of resistance 43; a grid leak 52 connected from the grid of the tube to ground; and an anode circuit connected from the anode of the tube to ground, serially including the input circuit of amplifier 45 and the anode To reduce the sensitivity of. portions of the apparatus to stray electrostatic fields there has been schematically shown electrostatic shielding 54, at frame or ground potential, surrounding the strip 4|, the resistance 43,

the condenser 49, the grid leak 52 and tube 44.

The illustrated embodiments of the invention are intimately concerned with the above mentioned for controlling the potential of each string with respect to ground. In introduction'to the description of these embodiments themselves it is appropriate to point out that upon string vibration the amplitude of the A. C. voltage across resistance 43, and hence of the output sound produced by loudspeaker 5 (excepting as deliberately modified by volume control 46) is proportional not only to the amplitude of string vibration but also to that of the charge in the string-to-strip 4! capacity, and hence to the mean D. C. potential across that capacity. Therefore by control of this mean potential it may be said that there is controlled the translation efiiciency of the mechanico-electric translating system, and more generically that of the mechanico-electro-acous-. tic translating system. A zero translation efficiency, an absence of A. C. voltage across resist-.

ance 43, and an absence of sound from loudspeaker 48 are the results of a lack of such potential; while a finite such efliciency and (a string being vibrated) a finite such voltage and sound each result from the existence of such mean potential, and are each proportional to its amplitude. This mean potential across each string-tostrip 4| capacity is identical (excepting for a time lag unnoticeable by the ear and resulting from the time constant of string-to-strip capacity with resistance 43) with the potential of that string with respect to ground. The control of. string potential with respect to ground will changed to' a. modified value upon associated key In the issued depression, or in other words upon the initiation of a cyclic digital operation comprising key depression and subsequent release; and was restored to its normal value upon the completion of the cyclic operation (i. e., .upon release of the key). According to the instant invention a potential of a normal value is again ordinarily supplied and is again gradually changed to a modified value i by the initiation of the cyclic digital operation;

but it is not necessarily restored to its normal value upon completion of that operation, but is therethrough and thereafter maintained at its modified value at will by selectively operable means, specifically pedals 2| and 26. The relative normal and modified values of potential may be varied according to the nature of output tone or sound which it is desired to produce. Attention is hereinafter called to several particular relations of these values adapted to produce a like number of particular sound natures.

In the various illustrated embodiments of this invention the means for controlling the potential of each string may be conveniently considered as comprising a common source of potentials; an individual reactive system associated with each string for rendering relatively gradual all changes of string potential; an individual normalizing circuit connected to each reactive system from a common point in the source and closed throughout substantial contact with the associated string of the associated damper; and a modifying" circuit connected to each reactive system from another common point in the source and closed throughout depression of the asosciated key. In each figure the common source is shown as a battery 6| having one of its terminals--the negative by way of illustration only-connected to ground by connection thereof to some portion of the frame I, and being shunted by a potentiometer 62 having movable contacts 63 and 64. At these two contacts may respectively terminate the normalizing circuits for all strings and the modifying circuits for all strings. These circuits themselves and the reactive systems, being shown as respectively different in different embodiments,

' are described separately for each of the Figures 1, 3 and 5. V

The reactive system associated with each string in Figure l is simply the condenser 81, an individual such condenser being connected from each string 5 to ground--i. e., to frame I. The associated normalizing and modifying circuits, being connected to the ungrounded side of this condenser, are thus in this particular embodiment also directly connected to the string; but it is convenient to consider the potentials supplied by these circuits as supplied to the reactive system and therefrom to the string. I

In Figure 1 the normalizing circuit for each string is provided as follows: The forward'portion of the damper 13 for each string, including the damping pad |2a,-is rendered electrically conductive by impregnation with a collodial graphite solution or emulsion. This impregnation may be efifected by a dipping and drying prpcess or a plurality of repeated. such processes rfi A purely surface impregnation of the solict andcustomarily wooden portion of the damper is sufficient; and while it is possible to illustrate only a surface impregnation of the damping pad itself, it is to be understood that as-to this part the impregnation is contemplated as desirably extending somewhat interiorly of the pad f'l'his pad is usually of wool felt; and a graphitejjsolution or emulsion whose gether with the immediately adjacent portion of 10 instead of normal lines.

vehicle is largely ammonia has been found to be particularly suited for the proper impregnation of such material as well as entirely satisfactory for other material. In the figures the impregna- 5 tion of surfaces appearing in elevation has been denoted by the covering of such surfaces with small dots, or with stippling; and the impregnation of surfaces appearing only as edges has been denoted by the showing of such edges as heavy Afterimpregnation the damper l 3 will be understood to offer to electrical potentials between the string and the rear edge 65 of the impregnated portion a finite resistance which is the lower the stronger be the impregnation of the portion as established by strength of It may be produced by painting on the side of 25 the damper .with a relatively weak solution of the impregnating material mentioned above or provided in any other convenient manner. The damper guide rail I5 through which/all the damper rods l4 pass is intended in this embodiment always to make electrical contact with the damper rods and is formed of metal or other electrically conductive material. Finally this guide rail is electrically connected to the contact 63. The normalizing circuit for each string as thus described most obviously meets the specification that it be completed throughout'substantial contact with the string of the associated damper.

In Figure 1 the modifying circuit for each string is provided as follows: The ungrounded side of each reactive system or condenser 81 is wired to a lug 61 retained under the screw 20 which secures the associated damper flange l8 to the rigid portion l9. Each assembly of damper flange l8 and damper lever I! is renderedserially conductive from the surface contacting with lug 61 to the bottom surface 69 of the lever II by impregnatiomas above described, of appropriate portions of the assembly including'that surrounding the pivot pin 68. The rear portion of each key extension 9 together with the thereto secured back check 10 are similarly impregnated to provide a conductive path from the surface to the leather facing 13. Next a conductive path is provided from the rear surface 11 of the hammer tail 16 to the bottom surface 18 of the hammer flange 19. This path may intermediately include the strip 80 of resistive material (conveniently produced as suggested for the resistive strip 66) 60 on the hammer shank 8i; and its terminal portions may be respectively provided by impregnating the entire hammer tail 16 together with the immediately adjacent portion of the shank 8| and impregnating the hammer flange. I9 to- -the thereto pivotally assembled shank 8|. Final- -ly at least the top portion 84 of the hammer flange rail 83, with which portion the surfaces 18 of all the flanges 19 make contact, may be made of 70 metal or other electrically conductive material and connected to the potentiometer contact 64. The impregnated portions of each modifying circuit as thus described are preferably sufficiently impregnated so that the total value of resistance 75 of each, serially considered, is low compared to the resistance value of the strip 80 includedin each circuit. Normally and as illustrated each modifying circuit is open, as surfaces 69 and 15 are not in contact with each other, and as surface 11 does notcontact with facing 13. These respective portions do contact, however, at times hereinafter described; and it is therefore convenient to consider the surfaces 69 and 15 as forming the elements of a normally open switch 85, andthe surface 11 and facing 13 as the elements of a normally open switch 86.

For convenience in consideration thereof, the circuit of Figure 1 has been condensed in Figure 2. Herein appears a string 5; the translating system portions 4l43; the potential source 6I62-- 6364; a reactive system comprising condenser 81; a normalizing circuit including the damping pad I2a, schematically shown, and a resistance 66', representing the total series resistance of the normalizing circuit and preferably principally made up of the resistance strip 66; and a modifying circuit including switches 85 and 86 (respectively comprising surfaces IS-69 and surface and facing ll-13) and the resistance 80 representingthe total series resistance of the modifying circuit with switches closed and preferably principally made up of the resistance of strip 88. The

' portions individual to a single string have been enclosed within a dotted line, and portions common to all the strings appear therewithout.

, With the key 8 associated with a given string 5 in normal or raised position, the normalizing circuit associated with that string hasbeen seen to be closed. The associated modifying circuit,however, is then open by virtue of the open condition of both switches 85 and 86. The given string 5 has the potential of contact 63, or its normal potential, with respect toground, During a downward movement of the associated key8, however, the associated switch 85 closes; and the associated damping pad I2a is lifted off the string, opening the associated normalizing circuit. The associated switch 86 is still open, however, as is consequently the modifying circuit containing it, and the string is therefore still without urge to change its previously existing normal potential. But almost immediately thereafter the associated hammer I strikes the string, rebounds, and effectively closes the switch 86 and hence the modifying circuit. The potential of contact 64-the modified potential for the string-is then presented through the modifying circuit to the reactive system 81. The capacity comprised in the reactive system requires time to change its charge through the resistance 80 of the modifying circuit, and this causes the string to assume the modified potential gradually rather than abruptly.

It will be appreciated that as long as the key remains depressed, and therefore the modifying circuit closed and the normalizing circuit open,

the string will be positively influenced to retain its modified potential.

During. the first portion of the upward movemerit of the key 8 attendant upon key release the associated switch 86 is opened, action mechanism H-being conventially arranged to move the hammer tall 16 out of contact with the back-check 10 at this time. This opens the modifying circuit (the later opening of its switch 85 being. therefore immaterial). Until justbefore the completion of the upward movement of thekeyihe contact of damper with string is of course prevented and the normalizing circuit is therefore maintained in an open condition. As long as thifs'condition exists, for whatever cause, the string is'without influence to change its potential from the modified value, which it therefore retains in spite of the opening of the modifying circuit. And this condition may be maintained at will by the appropriate use of either pedal, which will be understood to hold the damper out of contact with the string throughout and after key release. brought into contact with the string, whether upon key release or upon the completion of a pedalling operation, the normal potential will be again presented to the reactive system; the time required by the reactive system to change its charge through the resistance 66' of the normalizing circuit causing the string to assume the normal potential gradually other than abrutly.

Typical, but in no sense restrictive, appropriate values of the resistance strips 80 and 66 and of condenser 81 in Figure 1 may be assigned as 3 to 4 megohms, to 1 megohm, and .05 to .1 microfarad, respectively. It will be understood that the two resistances 8D and 66, each considered in connection with the condenser 81, are the determinants of the rate of assumption by the string of the modified and normal values of potential, respectively, when these potentials are presented to the reactive system. The lower the valve of either resistance the more rapid will be the corresponding such rate, while the lower the value of the capacity the more rapid will be both such rates- If either rate be made too rapid some extraneous noises may be produced by the loudspeaker upon the closing of either modifying or normalizing circuit; but in general a somewhat lower value of 66 then of 80 has been found permissible, as well as desirable in order that the re-assumption of normal potential value by the string may take place at-a rapid rate.

In Figure 1 there have been included two dotted lines A--A and BB. In further embodiments of the invention the apparatus illustrated in Figure 1 to 'the left of line A-A and to the right of the line B--B may be employed without change; and therefore in Figures 3 and 5, illustrating these further embodiments, only the instrument portion included between these two lines has been shown. Even in this illustrated portion much of the instruments of each of Figures 3 and 5 remains identical with that of Figure Land the description of these figures assumes this identity of parts similarly shown and not specially described. With this in mind reference is directed to Figure 3. The essential points of difference of the instrument of Figure 3 from that of Figure 1 are the elaboration of the reactive systems for the more positive elimination of the mentioned extraneous noises without as definite a restriction of choice of string potential change rates; and the re-arrangement of the normalizing circuits, including the arrangement of a portion of each co-extensively with a portion of the associated modifying circuit.

Each reactive system in Figure 3 includes not only the condenser 81 connected from string to ground, but also the resistance 88 having one extremity connected to the string, and a condenser 89 connected from the second extremity of the surface of damper flange l8 contactingwithlug 81 When the damper is again i to the bottom surface 69 of the damper lever l1. There may be optionally included in this path, however, a resistance strip 98, painted for example on the side of lever l1. The balance of each modifying circuit is provided identically as in Figure 1.

The balance of each normalizing circuit may be described as follows: Below the bottom surface 69 of each damper lever I1 is provided an individual carbon or other contact member 9|, this being arranged to contact with an impregnated portion of the associated surface 89 only when the associated damper I3 is in substantial con tact with its string. Each contact member 9| is permanently connected to the contact 63 of the potentiometer 62. In Figure 3, and more detailedly in the cross-sectional Figure 3a, there is shown an arrangement for supporting a contact member 9| to make the desired contact without significantly interfering with the customarily desired positive mechanical seating of the associated damper on its string. Thus an individual long metallic screw 92 is threaded through the base 33 under each damper lever i1 and through a common conductive member 93. Partially threaded into the upper end of each screw is an inverted cup member 94, and the carbon or other contact member 9| is made in the form of a button of inverted T-section protruding through a suitable aperture in the top of cup member 94. A coil spring 96 may bias the contact member 9| to its upmost position. This bias may be adjusted to l the weakest dependable value by rotation of the cup member 94 with respect to the screw 92, and this adjustment looked as by lock nut 95. Each entire assembly may be adjusted, just dependably to contact with theassociated surface 69 when the associated damper contacts with its string, from underneath the base 33 by rotation of the screw 92. The common conductive member 93 is wired to the potentiometer contact 63.

The circuit of Figure 3, condensed as wasthat of Figure 1 in Figure 2, is presented in Figure 4.

Herein appear a reactive system 89-88-81; a

As before, with the key 8 associated with a give en string 5 in a normal or raised position, the

normalizing circuit associated with that string is obviously closed, the associated modifying circuit open, and the string at its normal potential. During a downward movement of the liey the associated switch 85 closes and the associated. surface 69 is moved upwardly out of contact with its-contact member 9|, opening the normalizing circuit. The associated modifying circuit is not closed, however, until the switch 86 therein closes;

then the modified potential is presented to the associated reactive system 89-f-88-+81. By virtue of the time required for the charge in the condensers to change through the resistances 80' and 99' and additionally for that in condenser 81 to change through resistance 88, the assumption by the string of the modified potential is again gradual. Again as long as the key remains depressed the normalizing circuit remains open and the modifying circuit closed and the string is positively influenced to retain its modified potential. And the action of the circuit upon key and/or pedal release is quite similar to that above described for Figures 1-2, it being appreciated that the switch 86 will always open before the normalizing circuit is closed by contact of surface -69 with the contact member 9|.

As in the case of Figure 1, the impregnation of various circuit portions is preferably such as to result in serial resistance values, excluding those of the localized resistances 80, 90 and 08, which are low compared to those of the localized resistances. Typical, but again'not restrictive, appropriate values of the circuit components for Fig. 3 may be assigned as l to 2 megohms for the total value of 80 and 90, serially considered; /2 to 1 .meghom for the total value of SI and 90; l to 2 megohms for the value of 88; and .01 to .02 microfarad for the value of each of condensers 81 and 89. As mentioned above resistance 90 may be omitted (i. e., theoretically short circuited) it is included in Figure 3 principally so that a high resistance for BI may be avoided if desired.

In both the embodiments of Figures 1 and 3 the normalizing and modifying circuits are largely carried by operating portions of the instrument conventionally provided. -In this connection it may be mentioned that in these embodiments the break in each modifying circuit produced by the switches 85 is not required for electrical purposes, but performs the highly useful function of permitting the removal from the rest of the instrument, without complicated electrical disconnections, of the keys 8 with their extensions 9,, the

action mechanisms I I, the hammers 1, etc., which portions are conventionally made in the form of a removable action unit. In the embodiment of Figure 5, however, the normalizing and modifying circuits are not carried by operating portions of the instrument, but may be incorporated in a separate unit which-is assembled into operative relation with the conventional instrument. It will be seen in that figurethat the various elements shown impregnated in the earlier figures are herein unimpregnated, and that lug 61 and conductive top portion 84 of hammer flange rail 83 have been omitted as being unnecessary. The

reactive system 89- 8881 of Figure 3 has been employed with each string.

The normalizing and modifying-circuit for each string are again provided with a co-extensive portion, in this instance optionally including the resistance b; and definitely including a flat.

spring member I01 connected to the reactive system, through the resistance 90b if employed.'

The balance of each of the several normalizing circuits includes a portion of a common felt or leatherjstrip I03 secured to the top of a common conductive member or plate II; the plate IOI and strip I03 being disposed above the strings and dampers, and running in a direction transverse to that of the strings and thus appearing in Figure 5 in section. The strip I03 is impregnated each damper I3. The plate "II is electricallyconnected to potentiometer contact 03; and thus the normalizing circuit for each string may be traced through a resistance 90b, through a spring member I01, through the vertical transverse resistance of the portion of common impregnated strip I03 beneath that spring, and through the plate IM to the potential source. I

The balance of the modifying circuit for each string is provided by positioning above the common impregnated strip I03, and on the opposite side of the spring members I01 therefrom, a second common impregnated strip I04. This may be secured to the bottom of a common conductive bar I05, which in turn may be in-sulatively mounted to common plate MI in any convenient manner. The common bar I05 is electrically connected to the potentiometer contact 64. If and when the forward extremity of a spring member I01 is raised-so that the spring member contacts with the impregnated strip I04 there is closed the associated modifying circuit, which may then be traced through a resistance 9012, through a spring member I01, through the vertical transverse resistance of the portion of common impregnated strip I04 above that member,

and through the bar I05 to the potential source.

strip I03 and into contact with strip I04, each damper I3 is provided at its top with a hex-headed screw I06. This is adjusted so that with theassociated key 8 fully depressed the screw I06 causes the associated spring member I01 just dependably to contactwith the bottom of strip I04; and the spacing between the bar I05 and the plate I 0| is in general such that when the associated key is fully released the top of screw I06 is but negligibly out of contact with the bottom of the associated spring member I01. It is contemplated that the sustaining pedal system will be adjusted, as by collar 24a, so that the thereby produceable raising of the dampers I3 will be insufficient to cause contact of any spring member I01 with the impregnated strip I04, though of course sufficient to lift all the dampers from out of contact with the strings v and all thespring members I01 from out of contact with strip I03.

It is further contemplated that the sostenuto pedal system will be adjusted, as by collar 29a,

so that the thereby produceable raising of a damper I3 above the position corresponding to full key depression will be limited to an amount permitted by the flexing of the associated spring member I 01 and by the compression of the portion of strip I04 immediately thereabove.

The circuit of Figure 5, condensed as have been those of preceding figures, is presented in Figure 6. Herein appears a reactive system 898881; a resistancea90b and spring member I01 forming a co-extensive portion for mutually associated normalizing and modifying circuits; the balance of a normalizing. circuit schematically shown as a contact I03" representing the top surface of common strip I03, and a resistance l03 representing the transverse resistance of the strip portion opposite a spring member I01: and the balance of .a modifying circuit schematically shown as a contact 104, representing the, bottom surface of common strip I04, and a resistance I04 representing the transverse resistance of the strip portion opposite a spring member I01. It is particularly obvious from this figure that each spring member I01 forms the pole of a single-pole double-throw switch normally biased to one (the lower) ofv its two throw adjustments, and movable (by the damper) to its other throw adjustment or to an intermediate adjustment.

As before, with the key 8 associated with a given string 5 in a normal or raised position, the normalizing circuit associated with that string is closed, the associated modifying circuit open, and the string at its normal potential. During a downward movement of key 8 the associated spring member I0! is raised from out of contact with the strip I03, opening the normalizing circuit. The modifying circuit is not closed, however, until that spring member 101 contacts with strip I04; This will be understood to occur just at the completion of key depression. In contrast to the operation in the embodiments of Figures 1 and 3, the closing of the modifying circuit is not as positively delayed beyond the instant of impact of hammer with string, but it is sufficiently late so that the associated'string is still at least substantially at its normal potential at the instant of hammer impact. When the modifying circuit is closed the string as before assumes the modified potential gradually, rather than abruptly, because of the reactive system 8988 --8'l and the resistance lM'--90b of the modifying circuit.

Again as long as a key remains depressed, and in this embodiment also as long as the associated damper is maintained raised by the sostenuto pedal 26 whether or not the key be maintained depressed, the associated normalizing circuit re-.

mains open and the associated modifying circuit closed, and the associated string is positively influenced to retain its modified potential.

During the first portion of the upward motion of the key attendant upon key release the modifying circuit is opened; but the normalizing circuit is still in an open condition, and as long as this condition exists the string retains its modified potential. This condition may be maintained at will by the appropriate use of the sustaining pedal 2|, which will of course maintain all spring members I01 out of contact with the strip I03. When of the circuit components for Figure 5 may be assigned as 1 to 2 megohms for the total value of HM and b, serially considered; to 1 megohm for the total value of I03 and 90b; 1 to 2 megohms for the value of 88; and .01 to .02 microfarad for the value of each of condensers 81 and 89. These values are analogous to those assigned above for analogous components of Figure 3; and the resistance 90b, analogous to the resistance 90 of that figure, may be optionally omitted as in that case if desired.

In each of Figures 1, 2, 3, and 5 the contact 63, to which all the normalizing circuits are connected, has been shown adjusted to the grounded extremity of potentiometer 52; and the contact 64, to which all the modifying circuits are connected, has been shown adjusted to the'opposite extremity of the potentiometer. Thus the normal potential of each string with respect to ground is zero and the modified potential is the maximum of the battery 6|. The normal translation efliciency is therefore zero and\ the modified efliciencyfinite; the instrument is therefore adjusted to produce an output tone whose inception is of gradually risingamplitude. These relavibrations from which they are translated.

tive values of potentials, or of efficiencies, are exemplary only; and there have been illustrated in Figures 4 and 6 other typical adjustments of these contacts producing other relative potential or efficiency values.

. In Figure 4 the two contacts 63 and 64 have both been shown adjusted to the ungrounded exand with the illustrated percussion excitation of the strings a generally piano-like tone will therefore be produced.

In Figure 6 the contact 63 has been shown adjusted to the ungrounded extremity of the potentiometer 62 and the contact 64 to an intermediate point thereon. Thus the normal potential of each string with respect to ground is'the maximum of the battery 6| and the modified potential is a fractional part of this maximum potential. The normal translation efficiency is therefore of a finite value, and the modified efficiency is a fractional part of such value. The output tones of the instrument will then be characterized by an early gradual amplitude reduction superimposed on any which may be inherent in the In this case it will be obvious that with an adjustment of the contact 64 to the grounded extremity of the potentiometer 62 this early amplitude reduction will extend to a substantially complete elimination of the tone at a fixed short time after its inception, producing an apparent extreme rate of decay.

Thus the adjustment of the contacts or of equivalent switches may serve to control the dynamic characteristics'of the tones; and by virtue of the improved circuit arrangements herein disclosed the sustaining and sostenuto pedals 2| and cific details of the illustrated embodiments thereof, and that the scope of the invention is intended to be expressed in the following claims.

We claim:-

1. The combination with a piano including a key, a pedal, and a string arranged for vibration upon and during key operation and for continuance of vibration during continued pedal operation after key release: of a translating system, normally possessing a given efficiency, for translating the vibrations of said string into electric oscillations; and means for causing said translating system to possess a difi'erentefficiency. said last mentioned means being responsive both to operation of said key and to said continued pedal operation.

2. The combination with a musical instrument brations of said vibrator into sound; and mean:

ondary vibration control means, and a vibrator said source; and means for-causing said trans? latingsystem to possess a different efliciency, said last mentioned means being responsive both to operation of said primarymeans and to said continued secondary means operation.

4. In combination in a musical instrument, a vibrator; means normally characterized by given .efliciency for translating vibration thereof into sound; a key operable at will to produce vibration of said vibrator; means responsive to key operation for investing said translatingmeans with a modified efficiency; and means operable at will, and influencing jointly said vibrator and said translating means, for continuing said vi=- bration and said modified efliciency after release of said key.

5. In combination in a musical instrument, a vibrator; vibration governing means therefor;

means for translating vibration thereof into a sound; and a pair of means for investing said translating means with respectively different eificiene ies, said two means being associated with said vibration governing means for discontinuous, alternate operation, and said translating 'means being arranged to retain each of said efllciencies until investment thereof with the other of said efficiencies.

6. In combination ina musical instrument, a mechanical source of oscillations; means for governing the operation thereof; means for translating sound from said source; and a pair of means for investing said translating means with respectively different efficiencies, said two means being associated with said governing means for discontinuous, alternate operation, and said translating means being arranged to retain each of said efficiencies until investment thereof with the other of said efliciencies. I

7. In combination in a musical instrument, a vibrator; vibration governing means therefor; and a pair of means for applying two different potentials to said vibrator, said two means being associated with said vibration governing means for discontinuous, alternate operation, and said vibrator being arranged to retain each of said two potentials thereto applied until application theretoof the other of said potentials.

8. The combinationwith a piano including a string, means for translating vibrations thereof into sound, vibration governing means therefor including a damper portion normally resting thereon, a key depressible to raise said damper,

and a pedal depressible to maintain said damper raised; ofmeans associated with said vibration governing means and with said damper portion thereof forcontrolling the translation efiiciency of said translating means, said controlling means being responsiveto both-said key and said pedal. I 9. In combination in a musical instrument, a vibrator; means operable at will to initiate vibration thereof and means operable at will to terminate such' vibration; means. normally characterized by an efficiency of given value for translating such vibration into sound; means for changing said efficiency to'a modified value upon operation of said vibration initiating means; and means associated with said vibration terminating means, and operative only upon operation thereof, for restoring said efficiency to said given value.

10. In combination in a musical instrument, a vibrator; means operable at will to initiate vibration thereof and means operable at will to terminate such vibration; means normally characterized by an efficiency of given value for translating such vibration into sound; means for changing said efiiciency to a modified value upon operation of said vibration initiating means;

. means associated with said vibration terminating means, and operative only upon operation thereof, for restoring said efficiency tov said given value; and means for rendering gradual each change of said efliciency.

11. In combination in a musical instrument, a vibrator and means for translating vibration thereof into sound, said means being arrangedto retain a value of translation efficiency once assumed thereby until positively influenced to assume another value of efliciency; means operable at will to initiate vibration of said vibrator and means operable at will to suppress such vibration; means associated with said last mentioned means, and operative only throughout the operation thereof,'for positively influencing said translating means to assume a normal value of eificiency; and means operative upon operation of said vibration initiating means for positively influencing said translating means to assume a, modified value of efficiency.

12. In combination in a musical instrument, a vibrator and means for translating vibration thereof into sound, said means being arranged to retain a value of translation eificiency once assumed thereby until positively influenced to assume another value of efliciency; means operable at will to initiate vibration of said vibrator and means operable at will to suppress such vibration; means associated with said last mentioned means, and operative only throughout the operation thereof, for positively influencing saidtranslating means to assume a normal value of efficiency; means operative upon operation of said vibration initiating means for positively influencing said translating means to assume a modified value of efliciency; and means for rendering gradual each change of value of said efficiency.

13. The combination with a musical instrument including a vibrator adapted to retain a potential assumed thereby until the application thereto of a different. potential, and vih fifiionsound translating means "therefor having an ef-' while said key is depressed for applying a modified potential to said vibrator.

14. The combination claimed in claim 13, further including a reactive system interposed between said vibrator and both said last-mentioned two means, iorrendering gradual each change 01' potential or said vibrator. 1

15. The combination claimed in claim 13, further including a pedal depressible to maintain said damper raised, whereby to maintain said vibrator at said modified potential after release of said key.

16. In combination in a musical instrument, a vibrator; vibration-sound translating means therefor; a damper normally resting on said vibrator; a key depressible to excite said vibrator and to raise said damper; a double-throw switch means associated therewith, and an electric cir- Y associated with said damper, having a pole biased to a first throw adjustment and adapted to be.

moved by raising of said damper to a second throw adjustment; and means respectively re-- sponsive to said two throw adjustments for establishing respectively diflerent efiiciencies of said translating means.

17. The combination with a piano including a plurality of strings lying substantially in a plane, a plurality of dampers respectively resting on said strings, a plurality of keys respectively adapted to raise said dampers and to initiate vibrations of said strings, and translating means associated with each string for translating vitive means and respectively adapted to be raised 5 by said dampers out of contact with said first conductive means and into contact with said second conductive means.

18. In a piano including a-string, translating cuit controlling said translating means: piano portions in fixed relation to the extremity of said string; a lever pivoted to said fixed portions; a damper connected to said lever for movement thereby and normally resting on said string; a removable mechanism adapted to occupy a predetermined position relative to said fixed portions, and including a key and a member adapted upon key depression to impingeupon and move said lever and .two electric circuit portions respectively associated with said mechanism and with said fixed piano portions, and respectively including conductive means on said member and on said lever, said two circuit portions being mutually connected through said two conductive means during key depression when said mechanism occupies said predetermined position.

19. In a piano including a string, translating means associated therewith, and an electric circuit controlling said translating means: a damper; a conductive portion included in said damper and normally resting on said string; means for. raising said damper and conductive portion from said string and for vibrating said string; and electric circuit control means including a switch iormed mutually by said conductive damper portion and said string.

20. In a piano including a string, translating "means associated therewith, and an electric cir- 

